The present invention relates to copper matrix composites reinforced with at least one of continuous, monofilament SiC or boron fibers.
A variety of relatively high strength materials (e.g., microcomposites such as Cuxe2x80x94Nb and Cuxe2x80x94Ag alloys) having relatively high electrical conductivity are known (see, e.g., xe2x80x9cStrength And Conductivity of Cuxe2x80x94Ag Microcompositesxe2x80x9d, Sakai, T. Asano, K. Inoue, and H. Maeda, pp. 477-488, Chapter IV, in Proceedings of xe2x80x9cHigh Magnetic Fields, Applications, Generation and Materialxe2x80x9d, Edited by H. J. Schneider-Muntau, Singapore, World Scientific, 1997. Typically, as the strength of such materials increases, their electrical conductivity decreases, and vice versa.
Uses of high strength materials having relatively high electrical conductivity include electromagnetic applications, such as pulse magnets, which are used in high field strength magnets. The conductors used in these magnets need to be capable of withstanding high stresses created by strong magnetic fields, as well as be capable of maintaining their strength at the elevated temperatures associated with the use of these magnets. Further, the conductor materials should have sufficiently flexible to be bent over a small radius of curvature (e.g., a radius of 10 mm or less. Typically, the conductors used in high field strength magnet applications need to have an average tensile strength, at about 25xc2x0 C., of at least 0.7-1.5 GPa.
There is a continuing need for materials that have both high strength and high electrical conductivity.
The present invention provides a copper matrix composite (CMC) article (comprising at least one layer of a plurality of at least one of continuous, longitudinally aligned (i.e., parallel alignment of the fibers along the length of the article), non-touching (i.e., individual longitudinally aligned reinforcing fibers do not touch due to the copper metal matrix between each of the reinforcing fibers), monofilament SiC or boron reinforcing fibers. Preferably, the CMC article has, at 25xc2x0 C., an average tensile strength of at least 0.7 GPa (more preferably, at least 0.8 GPa; even more preferably, at least at least 0.9 GPa, and most preferably, at least 1 GPa, 1.25 GPa, 1.5 GPa, 1.6 GPa, or even 1.65 GPa). The average electrical conductivity of the CMC article preferably is at least 50% IACS (more preferably, at least 55% IACS; even more preferably, at least 60% IACS, or even at least 70% IACS; and most preferably, at least 75% IACS). Preferably, CMC articles according to the present invention are at least about 20 meters, and more preferably at least about 30 meters in length, although longer lengths may be desirable for certain applications.
Typically the CMC according to the present invention is elongated (typically having a length of at least 100 (preferably, at least 1,000, or even 10,000) times its thickness; wherein the length is at least 3 meters) and is continuous in length (i.e., having a length of at least 1 meter, preferably, at least 3 meters, more preferably, at least 10 meters).
In one aspect, the present invention provides a copper matrix composite article (typically, an elongated, continuous copper matrix composite article) comprising at least one layer of a plurality of at least one of continuous, longitudinally aligned, non-touching, monofilament SiC or boron reinforcing fibers, wherein the elongated article has, at 25xc2x0 C., an average tensile strength of at least 0.7 GPa (preferably, at least 0.8 GPa; more preferably, at least 0.9 GPa, and most preferably, at least 1 GPa, 1.25 GPa, 1.5 GPa, 1.6 GPa, or even 1.65 GPa) and an electrical conductivity of is at least 50% IACS (preferably, at least 55% IACS; more preferably, at least 60% IACS, or even at least 70% IACS; and most preferably, at least 75% IACS), and wherein the copper of the copper matrix has an average grain size of greater than 10 micrometers (in some case greater than 15 micrometers, greater than 20 micrometers, greater than 25 micrometers, greater than 30 micrometers, greater than 40 micrometers, even greater than 50 micrometers; typically in the range from greater than 10 micrometers up to 150 micrometers; more typically in the range from greater than 10 micrometers up to 55 micrometers).
In another aspect, the present invention provides, copper matrix composite article (typically, an elongated, continuous copper matrix composite article) comprising at least one layer of a plurality of at least one of continuous, longitudinally aligned, non-touching, monofilament SiC or boron reinforcing fibers, wherein the elongated article has, at 25xc2x0 C., an average tensile strength at least 0.7 GPa (preferably, at least 0.8 GPa; more preferably, at least at least 0.9 GPa, and most preferably, at least 1 GPa, 1.25 GPa, 1.5 GPa, 1.6 GPa, or even 1.65 GPa) and an electrical conductivity of at least 50% IACS (preferably, at least 55% IACS; more preferably, at least 60% IACS, or even at least 70% IACS; and most preferably, at least 75% IACS), and wherein the elongated article is capable of retaining at least 90 percent (preferably at least 95 percent; more preferably, 100 percent of its average tensile strength (measured at 25xc2x0 C.) and/or increasing its electrical conductivity, after being annealed for 3 minutes at 850xc2x0 C. in an argon environment with less than 5 ppm oxygen and less than 10 ppm water. Preferably, the increase in electrical conductivity after annealing is at least 1% IACS, more preferably 2% IACS, and even more preferably 4% IACS.
Copper matrix composite articles according to the present invention are useful, for example, in high field pulsed magnet applications.